Looking for help figuring out 11:1
Looking for help figuring out 11:1 I have a stock ls2 out of a 2006 vette. I will be running GM LS3 heads that are 69cc and would like to be 11:1 static compression without changing pistons.
I believe stock was 10.9 with the stock ls2 heads and stock head gasket of .051 thickness.
So with the bigger chambers what head gasket would get me there?
thanks
I believe stock was 10.9 with the stock ls2 heads and stock head gasket of .051 thickness.
So with the bigger chambers what head gasket would get me there?
thanks
you are adding 4.5cc of chamber volume, so there is no way you can now thin the head gaskets enough to get that back without the pistons crashing into the head. With the large 2.165" intake valves, milling the heads reduces the size of the intake lobe (cam) that will fit without hitting the piston.
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Joined: Jul 2007
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From: Wilmington, De
You would be at 10.5, I believe. Maybe even a little under.
And bullshit that you'll need new pistons. There are plenty of people who milled those heads .030" with stock gaskets and had a cam made that didn't require new pistons.
And bullshit that you'll need new pistons. There are plenty of people who milled those heads .030" with stock gaskets and had a cam made that didn't require new pistons.
running a .040" gasket and milling the heads .010" I calculated about 10.85-10.9 range compression ratio, depending if you figure a bit of primary ring-up-volume around the piston.
I'd stay short on the intake lobe to not cause PTV clearance issues. The Brian Tooley stage one LS3 cam would be my choice or something similar.
EPS and Tick can also get you a nice custom camshaft
I'd stay short on the intake lobe to not cause PTV clearance issues. The Brian Tooley stage one LS3 cam would be my choice or something similar.
EPS and Tick can also get you a nice custom camshaft
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Verdad Gallardo running a .040" gasket and milling the heads .010" I calculated about 10.85-10.9 range compression ratio, depending if you figure a bit of primary ring-up-volume around the piston.
I'd stay short on the intake lobe to not cause PTV clearance issues. The Brian Tooley stage one LS3 cam would be my choice or something similar.
EPS and Tick can also get you a nice custom camshaft
I'd stay short on the intake lobe to not cause PTV clearance issues. The Brian Tooley stage one LS3 cam would be my choice or something similar.
EPS and Tick can also get you a nice custom camshaft
TECH Fanatic
Joined: Jul 2007
Posts: 1,802
Likes: 333
From: Wilmington, De
With the large 2.165" intake valves, milling the heads reduces the size of the intake lobe (cam) that will fit without hitting the piston.
Now the exhaust valve is the one that's open fully as the piston is rushing towards it on the exhaust stroke, so that's the one that's going to run into PTV issues with too much duration and lift.
uncut LS3 heads can usually only safely fit a 230-232 duration intake lobe
I know people have fit larger but have knowingly accepted the consequences for running tighter than .060"/.080" PTV
My thoughts for your combo was to run the thinner gasket for tight quench which helps when you can't have the desired compression ratio, a clean up cut of .010" on the heads just to try to get you back to factory LS2 compression rating and then run a 224 intake lobe as the huge LS3 runner doesn't need a ton of duration to get a bunch of air in there.
Since you already have the 227 cam and Martin knows exactly what will fit safely and not, just run the 040 gasket and double check the clearances as I suspect both valves will be quite close.
The intake duration and lift of the cam has EVERYTHING to do with PTV (LS camshafts have a huge lift and fast ramp rates). The intake valve is pretty much getting off its seat when the piston is at 7 degrees ATDC and PTV is most needed. By the time the valve is at full lift, the piston is looong gone down the cylinder.
Now the exhaust valve is the one that's open fully as the piston is rushing towards it on the exhaust stroke, so that's ALSO the one that's going to run into PTV issues 7 degrees BTDC with too much duration and lift.
Now the exhaust valve is the one that's open fully as the piston is rushing towards it on the exhaust stroke, so that's ALSO the one that's going to run into PTV issues 7 degrees BTDC with too much duration and lift.
going to check the clearances. according to the machine shop there are a few scratches on the head surface so they want to clean them. I told them I can't go .010 not even .005. Wonder if I should just leave them
Martin is correct....do not mill if you are using the .040 gasket
uncut LS3 heads can usually only safely fit a 230-232 duration intake lobe
I know people have fit larger but have knowingly accepted the consequences for running tighter than .060"/.080" PTV
My thoughts for your combo was to run the thinner gasket for tight quench which helps when you can't have the desired compression ratio, a clean up cut of .010" on the heads just to try to get you back to factory LS2 compression rating and then run a 224 intake lobe as the huge LS3 runner doesn't need a ton of duration to get a bunch of air in there.
Since you already have the 227 cam and Martin knows exactly what will fit safely and not, just run the 040 gasket and double check the clearances as I suspect both valves will be quite close.
uncut LS3 heads can usually only safely fit a 230-232 duration intake lobe
I know people have fit larger but have knowingly accepted the consequences for running tighter than .060"/.080" PTV
My thoughts for your combo was to run the thinner gasket for tight quench which helps when you can't have the desired compression ratio, a clean up cut of .010" on the heads just to try to get you back to factory LS2 compression rating and then run a 224 intake lobe as the huge LS3 runner doesn't need a ton of duration to get a bunch of air in there.
Since you already have the 227 cam and Martin knows exactly what will fit safely and not, just run the 040 gasket and double check the clearances as I suspect both valves will be quite close.
I'd even bet that he can tell you within .005" of what your clearances will be depending on your valve springs, timing chain, and whether or not the heads have had a valve job or not.
here's one for you guys
on my previous build I hade different size pushrods from driver side to passenger. 7.40 and7.325. Same heads, same head gaskets, etc. Had the heads checked and machine shop says they are identical and valve stem height is the same as well.
to the best of my knowledge the short block has never been touched. why the heck difference?? cam profile? why?
on my previous build I hade different size pushrods from driver side to passenger. 7.40 and7.325. Same heads, same head gaskets, etc. Had the heads checked and machine shop says they are identical and valve stem height is the same as well.
to the best of my knowledge the short block has never been touched. why the heck difference?? cam profile? why?
here's one for you guys
on my previous build I hade different size pushrods from driver side to passenger. 7.40 and7.325. Same heads, same head gaskets, etc. Had the heads checked and machine shop says they are identical and valve stem height is the same as well.
to the best of my knowledge the short block has never been touched. why the heck difference?? cam profile? why?
on my previous build I hade different size pushrods from driver side to passenger. 7.40 and7.325. Same heads, same head gaskets, etc. Had the heads checked and machine shop says they are identical and valve stem height is the same as well.
to the best of my knowledge the short block has never been touched. why the heck difference?? cam profile? why?
cam tunnel not centered over the crankshaft which makes one set of lifters sit higher relative to the deck height